Method for monitoring the position of a semiconductor processing robot

ABSTRACT

A robotic positioning system that cooperates with a sensing system to correct robot motion is provided. The sensing system is decoupled from the sensors used conventionally to control the robot&#39;s motion, thereby providing repeatable detection of the robot&#39;s true position. In one embodiment, the positioning system includes a robot, a controller, a motor sensor and a decoupled sensor. The robot has at least one motor for manipulating a linkage controlling the displacement of a substrate support coupled thereto. The motor sensor is provides the controller with motor actuation information utilized to move the substrate support. The decoupled sensor provides information indicative of the true position the substrate support that may be utilized to correct the robot&#39;s motion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 10/697,731, filed Oct. 29, 2003 (APPM/7954), whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to robots suitable for usein semiconductor processing systems.

2. Background of the Invention

The modern semiconductor processing system typically includes a centraltransfer chamber surrounded by a plurality of processing chambers. Thecentral transfer chamber is generally coupled to a factory interface byone or more load lock chambers suitable for transferring the substratebetween the vacuum environment of the transfer chamber and the generallyatmospheric environment of the factory interface. The factory interfacetypically contains one or more substrate storage cassettes for stagingprocessed and unprocessed substrates.

Accurate and repeatable substrate transfer using the robots of thesemiconductor processing system is essential to ensure the processingresults, to reduce damage to substrates and processing equipment, and toenhance repeatability between substrates.

FIG. 7 depict one embodiment of a typical single-blade substratetransfer robot 700 utilized in many semiconductor processing systems.The robot 700 includes a blade 710 for supporting a substrate 712 duringtransfer. The blade 710 is coupled to a body 704 by a linkage 702. Thelinkage comprises a first arm 706 and a second arm 708 that are coupledto the body at a first end and coupled to a wrist 714 at a second end.The wrist is coupled to the blade 710. Each arm 706, 708 is coupled to arespective motor (not shown) concentrically stacked within the body 704.The positioning of the blade 710 is determined by the relative angularpositioning of the respective arms 706, 708 by the concentricallystacked motors. For example, if the linkages 706, 708 are rotated by theconcentrically stacked motors in the same direction about the centralaxis 720 of the body 704, the blade 710 is rotated about the centralaxis 720 as shown by the arrow 716. If the first arm and second arm 706,708 are rotated in opposite directions, the blade 710 is radiallyextended or retracted, as shown by arrow 718.

However, the ability to accurately position the blade 710 may becompromised by a number of factors. For example, the linkage 702 and/orthe blade 710 may become bent during handling or maintenance procedures.Additionally, thermal expansion of the linkage or loosening of the beltscommonly used within the linkage may result in positional drift of theblade. Thus, the blade may not arrive in the position expected based ona calculated movement of the arm. As these aforementioned problemsundesirably diminish the ability for efficient and repeatable substratetransfer, it would be desirable to improve the positional accuracy ofthe robot blade.

Therefore, there is a need for a method and apparatus for monitoring theposition of a substrate transfer robot.

SUMMARY OF THE INVENTION

A robotic positioning system that cooperates with a sensing system tocorrect robot motion is provided. The sensing system is decoupled fromthe sensors used conventionally to control the robot's motion, therebyproviding repeatable detection of the robot's true position. In oneembodiment, the positioning system includes a robot, a controller, amotor sensor and a decoupled sensor. The robot has at least one motorfor manipulating a linkage controlling the displacement of a substratesupport coupled thereto. The motor sensor provides the controller withmotor actuation information utilized to move the substrate support. Thedecoupled sensor provides information indicative of the true position ofthe substrate support that may be utilized to correct the robot'smotion.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features, advantages andobjects of the present invention are obtained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the impended drawings. It is to be noted,however, that the appended drawings illustrate only typical embodimentsof this invention and are, therefore, not be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

FIG. 1 is a plan view of an exemplary substrate processing systemincluding at least one robot having at least one decoupled robotposition sensing system;

FIG. 2 is a side view of the factory interface illustrating oneembodiment of a robotic positioning system that depicts the interfacebetween a substrate transfer robot and a sensing system;

FIG. 3 depicts a sectional view of one embodiment of the sensing systemdepicted in FIG. 2;

FIG. 4 is a side view of another sensing system;

FIG. 5 is a bottom view of one embodiment of a bracket of the sensingsystem of FIG. 4;

FIG. 6 is a bottom view of another embodiment of a sensing system havingsensors mounted to a ceiling of a factory interface; and

FIG. 7 (prior art) is a plan view of an exemplary substrate transferrobot suitable of a conventional substrate transfer robot suitable foruse in a semiconductor processing system.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

FIG. 1 depicts one embodiment of a semiconductor processing system 100having at least one robotic positioning system 150. The exemplaryprocessing system 100 generally includes a transfer chamber 102circumscribed by one or more processing chambers 104, a factoryinterface 110 and one or more load lock chambers 106. The load lockchambers 106 are generally disposed between the transfer chamber 102 andthe factory interface 110 to facilitate substrate transfer between avacuum environment maintained in the transfer chamber 102 and asubstantially ambient environment maintained in the factory interface110.

The transfer chamber 102 defines an evacuable interior volume 116through which substrates are transferred between the process chambers104 coupled to the exterior of the transfer chamber 102. The processchambers 104 are typically bolted to the exterior of the transferchamber 102. Examples of process chambers 104 that may be utilizedinclude etch chambers, physical vapor deposition chambers, chemicalvapor deposition chambers, ion implantation chambers, orientationchambers, lithography chambers and the like. Different process chambers104 may be coupled to the transfer chamber 102 to provide a processingsequence necessary to form a predefined structure or feature upon thesubstrate surface.

The load lock chambers 106 are generally coupled between the factoryinterface 110 and the transfer chamber 102. The load lock chambers 106are generally used to facilitate transfer of the substrates between thevacuum environment of the transfer chamber 102 and the substantiallyambient environment of the factory interface 110 without loss of vacuumwithin the transfer chamber 102. Each load lock chamber 106 isselectively isolated from the transfer chamber 102 and the factoryinterface 110 through the use of slit valves (not shown).

A controller 170 is coupled to the system 100 to control processing andsubstrate transfers. The controller 170 includes a central processingunit (CPU) 176, support circuits 174 and memory 172. The CPU 176 may beone of any form of computer processor that can be used in an industrialsetting for controlling various chambers and subprocessors. The memory172 is coupled to the CPU 176. The memory 176, or computer-readablemedium, may be one or more of readily available memory such as randomaccess memory (RAM), read only memory (ROM), floppy disk, hard disk, orany other form of digital storage, local or remote. The support circuits174 are coupled to the CPU 176 for supporting the processor in aconventional manner. These circuits include cache, power supplies, clockcircuits, input/output circuitry, subsystems, and the like.

A first transfer robot 160 is disposed in the factory interface 110 andis adapted to transfer substrates 112 between at least one substratestorage cassette 114 coupled to the factory interface 110 and the loadlock chambers 106. Each cassette 114 is configured to store a pluralityof substrates therein. One example of a factory interface that may beadapted to benefit from the invention is described in U.S. patentapplication Ser. No. 09/161,970 filed Sep. 28, 1998 by Kroeker, which ishereby incorporated by reference in its entirety.

A second robot 108 is deposed in the transfer chamber 102 and is adaptedto transfer substrates 112 between the processing chambers 104 and theload lock chambers 106. The second substrate transfer robot 108 mayinclude one or more blades utilized to support the substrate duringtransfer. The second robot 108 may have two blades, each coupled to anindependently controllable motor (known as a dual blade robot) or havetwo blades coupled to the second robot 108 through a common linkage. Inone embodiment, the transfer second robot 108 has a single blade 130coupled to the second robot 108 by a (frog-leg) linkage 132.

The first transfer robot 160 may include one or more blades utilized tosupport the substrate during transfer. The first transfer robot 160 mayhave two blades, each coupled to an independently controllable motor(known as a dual blade robot) or have two blades coupled to the firstrobot 160 through a common linkage. In one embodiment, the first robot160 has a single blade 140 coupled to a body 142 of first robot 160 byan articulated linkage 144. A motor (not shown), housed within the body142 controls the range of motion of the blade 140 about a central axis146 of the robot 160.

To increase the range of motion of the first robot 160, the body 142 iscoupled to a guide 138 that is selectively positioned along a rail 136by an actuator 134. The actuator 134 may be any motion device suitablefor positioning the first robot 160 along the rail 136, thereby movingthe central axis 146 within the factory interface 110 to facilitateaccess of the blade 140 to substrates within any of the cassettes 114 orload lock chambers 106. The actuator 134 is generally interfaced with anon board sensor 128, for example a rotary encoder, which provides thecontroller 120 with a derived positional information of the body 142along the rail 136. The derived position is a position based on ananticipated motion resulting from a predefined actuation. For example,as the body 142 is expected to move a predefined distance per motorrevolution, information provided by the sensor 128 may be utilized todetermine a change in position of the body 142. Referenced from acalibrated position stored in the memory of the controller 170, theanticipated position of the body 142 may be derived by knowing the motormotion and/or positional information provided by the sensor 128.Alternatively, the may be another sensor for providing informationindicative of the linear displacement of the body 142, such as a lineardisplacement transducer and the like.

At least one of the robots 160, 108 is interfaced with a sensing system120 to comprise a robotic positioning system 150. The sensing system 120provides information to monitor and/or correct the position of therobot. Although the robotic positioning system 150 shown to include thefirst transfer robot 160 disposed in the factory interface 110 of theexemplary processing system 100, the robotic positioning system 150 maybe configured to include the second robot 108. It is also contemplatedthat it is desirable to adapt the robotic positioning system 150 for usewith other robots utilized in other processing systems or semiconductorFABs, wherever accurate robot positioning and correction is desirable.

In the embodiment depicted in FIG. 1, the first transfer robot 160 isinterfaced with the sensing system 150 such that the positional accuracyof the first transfer robot 160 may be determined and corrected usingone or more sensors decoupled from the sensors on board the robotconventionally used to control the robot's motion. The sensing system150 includes at least one sensor 122 decoupled from the robot 160 andconfigured to provide a metric indicative of a true position of therobot 160. The true position is a position based on the actual positionof the robot 160.

In the embodiment depicted in FIG. 1, the sensing system 150 isconfigured to provide a metric indicate of the true position of thecentral axis 136. The sensing system 150 provides the controller 120with the true position which is compared with the derived position. Ifthe true and derived positioned are equivalent, then the body 142 andcentral axis 136 of the first robot 160 is accurately positioned. If thetrue and derived positioned are not in agreement, the controller 120then resolves a motion correction it the motor instructions such thatthe corrected derived position returns the body 142 to the trueposition. In this manner, the central axis 136 of the first robot 160may be accurately and repeatably positioned. Moreover, the metricprovided by the decoupled sensor 122 is transparent to the motion of thefirst robot 160 during normal operation, the motion of the robot 160 maybe monitored and corrected in-situ, without the need to interruptprocessing to run calibration procedures.

FIG. 2 is a side view of the factory interface 110 illustrating oneembodiment of an interface between the first transfer robot 160 and thesensing system 120 comprising the robotic positioning system 150. Thesensing system 120 generally includes sensor 122 and a flag 202. The atleast one of the sensor 122 or flag 202 is coupled to the factoryinterface 110 and is fixed relative to the central axis 146 of the firstrobot 160. In the embodiment depicted in FIG. 2, the sensor 122 iscoupled to the factory interface 110 and the flag 202 is coupled to theguide 138 supporting the robot body 142 on the rail 136.

The sensor 122 is fixed in a position where the flag 202, when passingthrough or within a predefined sensing field of the sensor 122, causesthe sensor 122 to change states. The position of the central axis 146within the factory interface 110 corresponding to where the sensorchanges states, known as a calibration position, is indicated by dashedline 204. Other reference positions of the central axis 146 within thefactory interface 110 corresponding to where the substrate exchanges (orother process requiring the blade 140 to be in a predefined position)are performed, known as a calculated or taught position, are shown bydashed lines 208. In the embodiment depicted in FIG. 2, the dashed lines208 indicate the position of the robot's axis 146 where transfersbetween the first robot 160 and load lock chambers 106 occur. Generally,the first robot 160 is programmed or taught to move to the taughtposition by instructing the robot to move a predefined distance (orrotation) as resolved by the on-board sensor 128. In other words,movement of the first robot 160 to the taught position is provided byenergizing the actuator 134 to move the robot 160 by rotating (in thecase of a motorized actuator) a number of rotations corresponding to adesired distance needed to reach the taught position as counted to theon-board sensor 128.

Since the on-board sensor 128 may accumulate positional error overrepeated movements or mechanical backlash and play within the motioncomponents, the first robot 160 may not arrive in the taught position asindicated by the dashed lines 208. To correct motion error or robotdrift, the sensor 122, which is decoupled from the mechanical linkagesof the robot 160 and other sources of drift, provides the controller 170with a metric indicative of the true position robot 160 at thecalibration position which is compared with the metric provided by theon board sensor 128. Differences between the expected position of thefirst robot 160 derived from the sensor 128 and the reference metrics atthe calibrated position are indicative of drift in robot motion, andprovide a metric to correct, e.g., recalibrate the robots movement, tothat data provided from the on board sensor 128 accurately positions thefirst robot in the taught positions.

The calibration position may be advantageously positioned between taughtpositions such that normal robot operations during processing passes theflag through the calibration position. Each time the flag passes throughthe calibration position, the robot motion may be recalibrated in-situ,thereby continually ensuring accurate robot positioning without need forseparate recalibration procedures.

FIG. 3 depicts a sectional view of one embodiment of the sensor 122 andflag 202 of the sensing system 120 depicted in FIG. 2. The sensor 122 iscoupled to factory interface 110 and provides the controller 120 with ametric of robot position at each change in sensor state. The sensor 122may include a separate emitting and receiving unit or may beself-contained such as “thru-beam” and “reflective” sensors. The sensor122 may be an optical sensor, a proximity sensor, mechanical limitswitch, video imaging device, Hall-effect, reed switch or other type ofdetection mechanism suitable for detecting the presence of the secondrobot 108 when in a predefined position. It is contemplated that a videoimaging device may provide metrics indicative of planar position alongwith elevation, thereby reducing the number of sensors required in asensing system. It is also contemplated that the sensor 122,particularly when embodying an optical sensor or video device, may belocated outside the factory interface 110 and positioned to view theflag 202, for example, through a window.

In one embodiment, the sensor 122 comprises an optical emitter 302 andreceiver 304. One sensor suitable for use is available from BannerEngineering Corporation, located in Minneapolis, Minn. The sensor 122 ispositioned such that flag 202, coupled to the second robot 108, guide138 or other component that moves with the robot central axis 146,interrupts a signal passing between the emitter 302 and receiver 304,such as a beam 306 of light. The interruption and/or return to anuninterrupted state of the beam 306 causes a change in state of thesensor 122. For example, the sensor 116 may have a 4 to 20 ma output,where the sensor 122 outputs a 4 ma in the uninterrupted state while thesensor outputs 20 ma in the interrupted state. Sensors with otheroutputs may be utilized to signal the change in sensor state.

FIG. 4 depicts another sensing system 400 that may be utilized in placeof, or in addition to, the sensing system 120 described above. Thesensing system 400 includes one or more sensors 402 disposed in a spacedapart relation to the first robot 160. The one or more sensors 402 maybe configured as similar to the sensor 122 described above. The sensors402 are oriented in a position that is fixed relative to the body 142 ofthe first robot 160. The sensors 402 are additionally positioned suchthat the blade 140 of the first robot 160 causes one or more of thesensors 402 to change state when moving between the interior of thefactory interface 110 and at least one of the load lock chambers 106 orcassettes 114 (as seen in FIG. 1).

In one embodiment, a bracket 404 is coupled to at least one of the guide138 or robot body 142. The bracket 404 provides a mounting surface forthe sensors 402. It is also contemplated that the bracket 404 be coupledto the robot 160 in a manner that allows the bracket 404 to rotate aboutthe central axis 146 such that the sensors 402 are maintained in radialalignment with the blade 140, thereby allowing positional metrics to beobtained with one sensor or group of sensors during the actuation of theblade 140.

Referring additionally to a bottom view of a portion of the bracket 404depicted in FIG. 5, the bracket 404 supports a first and at least asecond decoupled sensors 502, 508 of the plurality of sensors 402. Thefirst decoupled sensor 502 is configured to provide a metric indicativeof the relative distance between the blade 140 and the bracket 404(shown by “D” in FIG. 4). The metric provided to the controller 170 maycompared to a metric of blade elevation provided by an on board sensor504 that provides feedback from the motion of an actuator 506 of thefirst robot 160 controlling the elevation of the blade 140. In oneembodiment, the on board sensor 504 is a linear displacement transduceror other sensor suitable to determine the change in elevation of theblade 140 as moved by the actuator 506. In this manner, drift ordifferences between the expected position of the blade 140 (i.e., theposition based on blade actuator motion as monitored by the on boardsensor 504) may be corrected using the actual position informationprovided by the decoupled sensor 502.

In the embodiment depicted in FIG. 5, the bracket 404 additionallysupports at least a second decoupled sensor 508 of the plurality ofsensors 402 which is configured to provide a metric indicative of therelative distance and/or angular orientation of the blade 140 to thecentral axis 146 of the first robot 160. The metric provided to thecontroller 170 may compared to a metric of blade position provided by anon-board sensor 510 that provides feedback from the motion of a motor(s)512 controlling the rotation and/or extension of the blade 140. In themanner, drift or differences between the expected position of the blade140 (i.e., the position based on robot motor motion as monitored by theon board sensor 510) may be corrected using the actual positioninformation provided by the decoupled sensor 508.

FIG. 6 is a bottom view of a sensing system 600 having sensors 602mounted to a ceiling 604 of a factory interface 110. The sensors 602 aregenerally configured similar to the sensors 402 described above, and arepositioned between a first factory interface robot 604 and a secondfactory interface robot 606. The robots 604, 606, configured similar tothe robot 160 described above, may be programmed to pass thererespective blades 140 through a calibration position (shown by thecenter line 610) below the sensors 602 to obtain true positional metricsthat may be utilized to correct the robots motion as described above.

Thus, a sensing system has been provided that cooperates with a roboticpositioning system to correct robot motion. The sensing system isdecoupled from the sensors used conventionally to control the robot'smotion, thereby providing repeatable detection of the robot's trueposition. The true position may be compared to an expected position tocorrect for drift and misalignment. Moreover, the sensing system may beadvantageously configured to allow for in-situ data acquisition andmotion correction, thereby eliminating the need for separaterecalibration procedures.

While the foregoing is directed to the illustrative embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method for correcting robotic motion, comprising: sensing an actualposition of a robot at a calibration position; comparing the actualposition of the robot with a calculated position corresponding to thecalibration position; and compensating for differences in the actualposition and calculated position
 2. The method of claim 1, wherein thestep of sensing further comprises: moving the robot laterally to ataught position; and causing the decoupled sensor to change state beforethe robot reaches the taught position.
 3. The method of claim 2, whereinthe step of sensing further comprises: moving a blade of the robot to ataught position; and causing the decoupled sensor to change state.
 4. Amethod for correcting robotic motion, comprising: obtaining a metricindicative of an actual position of a blade of a robot at a firstposition with a sensor decoupled from the robot; comparing the actualposition of the robot with an expected position derived from a sensorcoupled to one or more robot actuators; and correcting robot motion inresponse to differences between the actual position and expectedposition.
 5. The method of claim 4, wherein the step of obtainingfurther comprises: moving the blade to a taught position; and causingthe decoupled sensor to change state.
 6. The method of claim 4 furthercomprising: obtaining a metric indicative of an actual position of ablade of a second robot at the first position with the decoupled sensor;comparing the actual position of the second robot with an expectedposition derived from a sensor coupled to one or more second robotactuators; and correcting second robot motion in response to differencesbetween the actual position and expected position.